Around the transition to middle school, preadolescents increasingly value peer relationships, yet report high rates of social anxiety and frequent experiences of peer exclusion and victimization. Self-report and physiological data confirm the distress associated with negative peer experiences in preadolescence. Parents typically recognize the challenges of peer relationships at this age, but parenting in the peer domain is surprisingly understudied, and many parents report uncertainty about how to help preadolescents in challenging social situations. Potentially, the effectiveness of parental efforts to support positive peer relationships is dependent upon individual child characteristics, such as preadolescents' physiological responses to the same social challenges that their parents wish to help them navigate. The proposed project will examine: (1) the predictive associations between parenting in the peer domain (facilitation, directing, problem-solving) before the middle school transition and preadolescent peer relations (friendship support, peer group acceptance, peer victimization) and psychological adjustment (depression, anxiety) at the end of the first year of middle school; (2) the predictive associations between preadolescent physiological responses to social challenges (skin conductance level, respiratory sinus arrhythmia) before the middle school transition and peer and psychological outcomes after the transition to middle school; (3) whether the predictive effects of parenting in the peer domain on preadolescent outcomes are moderated by preadolescent physiological responses, controlling for initial levels of adjustment. The short-term longitudinal design will involve two waves of data collection approximately one year apart. The sample will consist of 220 participants from two cohorts of fifth and sixths graders with high representation of racial/ethnic minorities. Preadolescents' physiological responses will be measured during peer social-evaluation (i.e., conversation with a research assistant while under evaluation by fictitious peer judges) and peer rebuff (i.e., feedback from fictitious peer judges that other participants performed better in the conversation) experiences in the lab. Parents, teachers, and preadolescents will report on peer relationships and psychological adjustment. Parents will also complete questionnaires that assess their facilitation (actively promoting positive interactions with peers) and directing (promoting interactions with peers based on parental values and preferences) of peer relationships, as well as open-ended questions that assess parental problem-solving in response to hypothetical peer problem situations. Hypotheses will be tested using structural equation modeling in MPlus. The proposed study will advance models that explain child developmental outcomes in terms of person by environment interactions, by applying this framework specifically to the peer domain. Results from the proposed study may also have significant applied implications by providing information about specific parenting practices that are matched (or mismatched) with child characteristics and support socio-emotional adjustment. PUBLIC HEALTH RELEVANCE: Given the prevalence of stress in peer relationships and related behavioral and mental health problems around the transition to adolescence, it is imperative to identify factors that may reduce the risk of maladjustment. Parental efforts to support positive peer relationships across the middle school transition may protect preadolescents against maladjustment, yet little is known about parenting strategies that are well- suited to preadolescents with certain forms of physiological susceptibility to social stress. The present study has the potential to advance knowledge and inform programs about parenting practices that may support preadolescents' social and emotional adjustment.